Thin film photovoltaic (PV) modules promise to be one of the leading edge power generation technologies of the twenty-first century. More and more attention is being drawn to the potential benefits of using thin film photovoltaic technology and, consequently, production of photovoltaic modules has risen in response to increased demand. However, a number of the metals needed to manufacture thin film photovoltaic modules are generally considered to be hazardous and can cause environmental health and safety hazards. An ever growing amount of manufacturing waste and disposal of photovoltaic modules accompanies the increased demand for photovoltaic technology and photovoltaic module production. The landfilling of superannuated photovoltaic modules and manufacturing waste associated with photovoltaic cells can release hazardous materials into the environment.
Some of the major elements or compounds used in photovoltaic cells are cadmium, selenium, tellurium and indium. Cadmium is the principal material used in the process of making photovoltaic cells, particularly CdTe modules, and is a secondary component in CIS (Copper Indium Diselenide) photovoltaic modules. The principal effects of continued exposure to low levels of cadmium are significantly apparent on the kidneys, lungs and bones. Cadmium may be fatal if inhaled and is also harmful if swallowed or absorbed through the skin. Prolonged exposure to cadmium can cause stomach pains, vomiting, diarrhea, lung irritation, chest pain and edema. The U.S. Environmental Protection Agency has concluded that the inhaled inorganic cadmium compounds are probable human carcinogens.
Tellurium may be fatal if inhaled, swallowed or absorbed through the skin. Inhalation of tellurium may result in fatality as a consequence of spasm, inflammation and/or edema of the larynx and bronchi, chemical pneumonitis and pulmonary edema. Exposure to tellurium can cause nausea, headache and vomiting.
The most primary regulatory test to evaluate the toxicity of photovoltaic manufacturing waste and superannuated modules is EPA TCLP (Toxicity Characteristic Leaching Procedure, 40 C.F.R. Ch. 1, Pt. 261, App. II). TCLP requires recycling processes to meet exacting standards.
CIS (Cadmium Indium Diselenide) photovoltaic modules generally contain between 5 and 14 g of Cd or Se per square meter of module. We have observed CdTe modules to contain between 7 and 12 g of Cd or Te per square meter of module. Additional sources of Cd and Te come from manufacturing debris from the fabrication of the photovoltaic modules. The manufacturing waste typically includes CdS, CdTe and various non-stoichiometric mixtures containing Cd, Te and Zn. The hazardous metals involved in photovoltaic module manufacturing and waste have high potential for impacting the environment.